1. FIELD OF INVENTION
This invention concerns a process and apparatus for the continuous manufacture of peroxyesters in high purity and at high through put per unit reactor volume.
2. STATE OF THE PRIOR ART
Peroxyesters, R-C(O)OOR', are extensively used as initiators in the polymerization field because they are efficient initiators. These peroxyesters, however, are highly temperature sensitive decomposing violently to the point of ignition at high temperatures. The presence of a large amount of peroxyester in a reaction mass only augments this problem; hence, extreme precautions are necessary to prevent accidents in the commercial batch processes when large quantities of the peroxyesters are produced. One precaution usually exercised in the preparation of peroxyesters is to use a solvent medium to ensure safe operation. The presence of solvents in the initiators, however, often affect their efficiency adversely in the polymerization processes.
An example of the prior art is U.S. Pat. No. 3,849,468 which describes a continuous process for the preparation of solutions of tertiary-butyl peroxyesters in a single closed-circuit reactor system; the acid chloride, the caustic, the t-butyl hydroperoxide and solvent are introduced into the system in the presence of an aqueous reaction support. In the system described, air is used to promote circulation of material in the closed loop. The mixing and interfacial contact between the reactants in the two phases are brought about by passing them and the reaction support through a packed column of Raschig rings. Such a system is inadequate for the efficient mixing essential for ensuring complete conversion of the acid chlorides, particularly the high molecular weight ones that are sluggish to react; hence this would result in an impure product containing a significant amount of the unreacted acid chloride. Also the presence of the reaction support decreases the effective volume for the reaction thereby reducing the throughput per unit volume of the reactor.
Since the use of solvents and aqueous reaction support decreases the efficiency of processing and since pure (undiluted) peroxyesters are desired for many polymerization processes, it would be highly desirable to have a continuous, solvent-free process which would increase processing efficiency yielding products of high quality at high throughputs and be capable of providing the polymerization industry with a choice of either pure or diluted products.